Modelling individual variability in cognitive development

Investigating variability in reasoning tasks can provide insights into key issues in the study of cognitive development. These include the mechanisms that underlie developmental transitions, and the distinction between individual differences and developmental disorders. We explored the mechanistic basis of variability in two connectionist models of cognitive development, a model of the Piagetian balance scale task (McClelland, 1989) and a model of the Piagetian conservation task (Shultz, 1998). For the balance scale task, we began with a simple feed-forward connectionist model and training patterns based on McClelland (1989). We investigated computational parameters, problem encodings, and training environments that contributed to variability in development, both across groups and within individuals. We report on the parameters that affect the complexity of reasoning and the nature of ‘rule’ transitions exhibited by networks learning to reason about balance scale problems. For the conservation task, we took the task structure and problem encoding of Shultz (1998) as our base model. We examined the computational parameters, problem encodings, and training environments that contributed to variability in development, in particular examining the parameters that affected the emergence of abstraction. We relate the findings to existing cognitive theories on the causes of individual differences in development

An investigation of the concept of balance in children ages 6–9: Logic and protologic identifiable in making mobiles

This research was conducted to explore children\u27s construction of protologic (foreshadowing of operations) in the context of experience with balance mobiles in a constructivist setting and to explore the usefulness of making mobiles in promoting children\u27s development of the concept of balance. The statement of the problem is (a) Can constructivist principles of cognitive development be used to understand children\u27s progress in the course of educational activities involving balance? If so, how? What does the progressive construction of notions about balance look like in children\u27s behaviors? and (b) Does children\u27s understanding of balance improve after experimenting with making mobiles? The participants in this study were 10 first grade children and 12 third grade children from a public elementary laboratory school located in Cedar Falls, Iowa. The pretest and posttest used a primary balance scale and a beam balance. Making mobiles was used as the intervention. The research of Piaget, Kamii, and Parrat-Dayan (1974/1980) and Inhelder and Piaget (1955/1958) were used as the basic framework for the pretest and posttest. All interviews and the dialogues during the tests and making mobiles were videorecorded and transcribed for analysis. Evidence of compensation and reversibility, coherence, coordination, and contradiction were assessed in children\u27s reasoning during intervention activities using operational definitions developed by Jean Piaget. Before the intervention, all children had an idea that weight impacts balance, 13 out of 22 children had the idea that distance from the fulcrum impacts balance, and 6 out of 22 children considered weight and distance at the same time. After the intervention, all children maintained the idea that weight is related to balance but more children, 16 out of 22, had the idea that distance is related to balance; and 6 children among the 16 children considered weight and distance at the same time. Through the three intervention activities, more children showed consistently their belief that the higher side needs more weight to making bars balance and the understanding of the idea that distance is related to make bars balance. Nine children experienced a “Eureka” moment, that is, they had a sudden insight about how to make bars of mobile balance or connected their prior experience to the current situation

Investigating the mechanisms underlying fixation durations during the first year of life: a computational account

Infants’ eye-movements provide a window onto the development of cognitive functions over the first years of life. Despite considerable advances in the past decade, studying the mechanisms underlying infant fixation duration and saccadic control remains a challenge due to practical and technical constraints in infant testing. This thesis addresses these issues and investigates infant oculomotor control by presenting novel software and methods for dealing with low-quality infant data (GraFIX), a series of behavioural studies involving novel gaze-contingent and sceneviewing paradigms, and computational modelling of fixation timing throughout development. In a cross-sectional study and two longitudinal studies, participants were eye-tracked while viewing dynamic and static complex scenes, and performed gap-overlap and double-step paradigms. Fixation data from these studies were modelled in a number of simulation studies with the CRISP model of fixation durations in adults in scene viewing. Empirical results showed how fixation durations decreased with age for all viewing conditions but at different rates. Individual differences between long- and short-lookers were found across visits and viewing conditions, with static images being the most stable viewing condition. Modelling results confirmed the CRISP theoretical framework’s applicability to infant data and highlighted the influence of both cognitive processing and the developmental state of the visuo-motor system on fixation durations during the first few months of life. More specifically, while the present work suggests that infant fixation durations reflect on-line perceptual and cognitive activity similarly to adults, the individual developmental state of the visuo-motor system still affects this relationship until 10 months of age. Furthermore, results suggested that infants are already able to program saccades in two stages at 3.5 months: (1) an initial labile stage subject to cancellation and (2) a subsequent non-labile stage that cannot be cancelled. The length of the non-labile stage decreased relative to the labile stage especially from 3.5 to 5 months, indicating a greater ability to cancel saccade programs as infants grew older. In summary, the present work provides unprecedented insights into the development of fixation durations and saccadic control during the first year of life and demonstrates the benefits of mixing behavioural and computational approaches to investigate methodologically challenging research topics such as oculomotor control in infancy

Testing mechanisms of development within a computational framework

Theories of development have proposed several mechanisms by which development occurs in children. The majority of the proposed mechanisms lack precise definitions, and are difficult to test individually whilst holding the effects of all other mechanisms constant. Implementing the mechanisms within a computational framework forces precision and enables the effect of each mechanism to be examined in isolation. A computational model of adult behaviour in a developmental task was created. The model included a range of the mechanisms proposed by theories of development, whereas previous computational models of development have examined very few mechanisms. The mechanisms were tested in the model both independently and in combination, with the results being compared against the behaviour of seven year old children on the task. The independent modifications showed that the behaviour of the model changes significantly for four mechanisms: strategy choice, strategy accuracy, capacity, and processing speed. The best mechanism (strategy accuracy), when applied to the adult model, matched seven out of nine regularities in the behaviour of seven year olds, including reaction time and errors. The combined modifications also matched seven year old children's behaviour. The results show that a range of developmental mechanisms can now be routinely tested and evaluated within a single computational model. The method of modifying computational models is an interesting way to examine the influences of developmental mechanisms, and therefore helps in answering "What develops in children?"

Modeling cognitive development on balance scale phenomena

We used cascade-correlation to model human cognitive development on a well studied psychological task, the balance scale. In balance scale experiments, the child is asked to predict the outcome of placing certain numbers of equal weights at various distances to the left or right of a fulcrum. Both stage progressions and information salience effects have been found with children on this task. Cascade-correlation is a generative connectionist algorithm that constructs its own network topology as it learns. Cascade-correlation networks provided better fits to these human data than did previous models, whether rule-based or connectionist. The network model was used to generate a variety of novel predictions for psychological research